The present invention relates generally to communication systems using wireless communication networks, and more particularly to methods and systems for supporting wireless communication on local area networks (LANs).
Operation of a wireless cellular communications network requires cooperation among a number of different elements. Wireless communication devices supported by these networks include cellular telephones, personal digital assistants (PDAs), and wireless computers. A base station is located within each cell of a cellular network for transmitting and receiving information to and from the wireless communication devices. Base station controllers are utilized to control clusters of base stations by providing the base stations with the information to transmit to mobile communication devices within the range of the base stations. Mobile switching centers route calls between base stations, other mobile switching centers, and the public switched telephone network.
Each mobile switching center is associated with a home location register and a visitor location register. The home location register stores the management data relating to all of the wireless communication devices in the network. The management data for any particular wireless communication device includes an international mobile station identity (IMSI), a profile of capacities and services of the wireless communication device, and the location of the wireless communication device within the cellular network.
Each wireless communication device is assigned to a particular home location register, and a subset of the IMSI assigned to the wireless communication device identifies the particular home location register to which the wireless communication device is assigned. If the wireless communication device visits a network other than its home network, it registers with the visitor location register of the visited network. When the wireless communication device is turned on in the visited network, the device""s IMSI is requested and passed onto the visitor location register. Using the IMSI, the visitor location register obtains the information required for registration of the device from the home location register assigned to the wireless communication device. Once the device has registered with the visitor location register, the device can place and receive calls in the same manner as if the device were located in its home network. However, each time the wireless communication device enters a visited network, the registration process must be repeated.
Additionally, every time a wireless communication device is operated, the profile is transmitted from the home location register to the visitor location register associated with the mobile switching center of the cell in which the wireless communication device is located. The messaging traffic between the home location register and the visitor location register can limit the call traffic handling capacity of the wireless communication network, because several messages must be exchanged between the home location register and the visitor location register before a call can be completed.
U.S. Pat. No. 5,590,175 to Gallant et al. proposes a solution to the reduced call traffic capacity of prior art cellular network systems. The solution includes selectively eliminating the need to access the home location register for those calls made to a wireless communication device having a home location at the same base station that is receiving the calls from the public switch telephone network. The visitor location register includes the profile of each local wireless communication device that has registered with the visitor location register. The profile includes a home location register query flag which determines whether access to the home location register is required for a particular call. If the query flag indicates that no access to the home location register is required, then the profile contains sufficient routing information to complete the call. If, on the other hand, the flag indicates that call forwarding or roaming information is required, the home location register must be contacted to obtain this information.
Although the Gallant et al. patent provides a partial solution to the call traffic capacity diminishment of a cellular telephone network, the substantial volume of messaging traffic resulting from the visitor location register accessing roaming information or call forwarding information from the home location register leaves room for improvement over the current system.
What is needed is a method and system for improving the efficiency of call message handling in wireless communication networks.
A system and method for supporting wireless communications within an internetwork enable decentralization of the support of individual wireless communication devices by utilizing dynamic internetwork protocol telephony addresses and by selectively using single-cast, multicast and broadcast techniques. The telephony addresses are fixed within a particular network of the internetwork, but are xe2x80x9cdynamicxe2x80x9d with respect to the networks, since each network may assign a different telephony address to a particular wireless communication device.
The internetwork is formed of a number of networks that are linked to exchange messages, requests and other signals. The internetwork may be formed of interlinked networks of a single business entity. Each network includes a base station having a generally fixed transmission region with respect to supporting communications with wireless communication devices, such as cellular phones, pagers and personal digital assistants (PDAs). Each network further includes a call control unit, such as a router-server, for establishing communication links and for assigning a dynamic telephony address in response to a registration request from a particular wireless communication device. The registration request is received via the base station of the network and includes a device identifier which is specific to the wireless communication device. The device identifier is universally applied within the internetwork, but the dynamic telephony address is assigned independently of assignments within other networks of the internetwork.
In the preferred embodiment, the dynamic telephony addresses are internet protocol (IP) telephony addresses. If the particular wireless communication device enters the transmission regions of each of the base stations within the internetwork and transmits registration requests via each of the base stations, the wireless communication device may be assigned a number of dynamic telephony addresses equal to the number of networks. The registration request may be automatically triggered by the wireless communication device merely by activating the device within a transmission range, but other triggering techniques may be utilized.
Each network includes memory having stored data that is representative of associations between each device identifier and the dynamic telephony addresses assigned by networks to the wireless communication device to which the device identifier is specific. When an incoming call is directed to a wireless communication device via a call control unit, if it is determined that the device is not within the transmission region of that network, the memory is accessed to determine which remotely assigned dynamic telephony addresses are available. If the network in which the device resides is known and the dynamic telephony address assigned by that network is also known, a single-cast call-setup message can be transmitted to the remote network. The message includes the dynamic telephony addresses assigned by that network, facilitating the process of establishing the communication link for the incoming call. If the location of the wireless communication device is not known, call-setup messages may be multicast to each remote network for which a dynamic telephony address is accessible within the local memory. Locate-wireless-communication-device messages may be multicast or broadcast to remote networks if none or only a portion of the remotely assigned dynamic addresses are accessible within the local memory. Such messages include the device identifier that is specific to the wireless communication device and a request for the dynamic telephony address associated with the device identifier.
In the preferred embodiment, the assignment of a dynamic telephony address to a wireless communication device is not followed by a broadcast of the assigned address to the remaining networks in the internetwork. Resources of the internetwork and the individual networks are conserved by communicating the different dynamic telephony addresses on an as-needed basis. However, with each communication of dynamic telephony addresses, the addresses are stored in local memory.